What you should know

The equipment used to support devices like loudspeaker clusters, lights etc should be fit-for-purpose.

Devices like loudspeaker clusters, lighting etc can weigh up to 500kg and are often suspended 6m or more above ground level.

Incorrect selection and adaptation of the equipment to support devices like speaker clusters at outdoor events has led to the equipment overturning and hitting people causing serious injuries. There have also been near misses when elevated devices exposed to the wind, have caused the mast of the supporting equipment to buckle and partially collapse.

Take steps to ensure the equipment will endure the prevailing environment:

Take account of foreseeable wind loading and any other relevant factors such as ground strength and slope.

There are a number of proprietary systems available from specialist contractors and suppliers, for use outdoors, designed so that the vertical truss section will accommodate the effects of wind loading. In most of these systems, there is a base of sufficient size, with sufficient ballast loaded onto the base, to provide for an appropriate factor of safety to prevent overturning. Some specialist structures rely on base area rather than ballast.

The use of ‘guy’ ropes may be necessary.

It may be possible to de-rate the equipment to take account of wind loads, i.e. use lifting equipment of greater capacity than the weight of the load.

Check to ensure the structure is build in accordance with the design and/or manufacturer’s instructions.

If the completed structure is susceptible to the weather, monitor and measure the local weather conditions. In adverse weather conditions, know what to do with the equipment to protect its stability. Where such arrangements are not in place, it may be prudent to provide an exclusion zone [in the order of 1.5 times the tower height] around the tower, in case the wind speed does exceed design-operating speeds and the equipment collapses.

It is essential that any ballast remains in place for the time that the structure is in use.

Have suitable measures in place to prevent unauthorised persons tampering with any winch or brake mechanisms and / or ballast. One way of doing this would be to erect a barrier or something similar around the base of the equipment. This would also help to reduce the risk of a member of the public climbing the structure and accidently falling.

Don'ts

Don’t use equipment intended exclusively for indoor use in an outdoor setting.

They are not generally designed to take account of wind loading. Usually, indoor equipment can only resist overturning in one principal direction eg to the front. Overturning to the rear or sides is likely even with minimal external loads.

Nor are they designed to take account of the additional bending forces, which can be a consequence of restraining the base or adding ballast and /or from out-of-plumb effects caused by erecting them on uneven ground.

Find out more

Further advice on the design of lifting equipment used in the entertainment sector is given in British Standard BS 7905-1: 2001 Lifting equipment for performance, broadcast and similar applications - Part 1: Specification for the design and manufacture of above stage equipment (excluding trusses and towers) and in BS 7905-2: 2000 Part 2:Specification for design and manufacture of aluminium and steel trusses and towers. (hyperlink to BSonline)